1. Field of the Invention
The present invention relates to a vibration-preventive support device which, when connecting and supporting two members one of which is movable with respect to the other, can prevent the vibration of one member from being transmitted to the other.
2. Description of the Related Art
Conventionally, a vibration-preventive support device for connecting and supporting two members in a vibration-preventive manner is structured, for example, in such a manner as shown in FIG. 7. That is as shown in FIG. 7, the conventional vibration-preventive support device comprises a large-diameter cylindrical portion 1, a small-diameter cylindrical portion 2 situated upwardly of the large-diameter cylindrical portion 1, a ring-shaped connecting portion 3 for connecting together the large-diameter cylindrical portion 1 and small-diameter cylindrical diameter cylindrical portion 1 and small-diameter cylindrical portion 2, and a ring-shaped flange portion 4 formed on the upper end portion of the small-diameter cylindrical portion 2. The large-diameter cylindrical portion 1, small-diameter cylindrical portion 2, ring-shaped connecting portion 3 and ring-shaped flange portion 4 are formed together in an integrally united body by molding elastic material such as rubber or the like, thereby producing a vibration-preventive support device 5.
Further, the small-diameter cylindrical portion 2, ring-shaped connecting portion 3 and ring-shaped flange portion 4 cooperate together in forming a fitting recess portion 7 having a U-shaped cross section, and there is formed a through-hole 11 in a movable member 10 which is capable of moving with respect to a fixed body 9; and, the portion of the movable member 10 that is situated in the peripheral edge of the through-hole 11 is fitted or inserted into the fitting recess portion 7 to thereby mount the movable member 10 onto the vibration-preventive support device 5. On the other hand, there is provided a boss 13 on the fixed member 9; and, the boss 13 is loosely fitted into the large-diameter cylindrical portion 1 and small-diameter cylindrical portion 2 from below, and a screw 15 with a washer 14 is threadedly engaged with the boss 13 to thereby mount the fixed member 9 onto the vibration-preventive support device 5.
In this state, within the large-diameter cylindrical portion 1 and outside the boss 13, there is arranged an auxiliary spring 17. Also, between the washer 14 and the flange portion 4 of the vibration-preventive support device 5, there is formed a clearance in consideration of the movement of the movable member 10.
However, since the above-described conventional vibration-preventive support device 5 is structured such that the movable member 10 is raised up by the large-diameter cylindrical portion 1 and small-diameter cylindrical portion 2 connected together by the connecting portion 3, in order to prevent the large-diameter cylindrical portion 1 and small-diameter cylindrical portion 2 from buckling, the auxiliary spring 17 is indispensably necessary; but, the existence of the auxiliary spring 17 makes it impossible to lower the natural vibration frequency of the vibration-preventive support device 5, which results in the lowered vibration damping performance thereof. Also, the auxiliary spring 17 gives rise to an increase in the number of parts, thereby leading to an increase in the manufacturing cost of the vibration-preventive support device 5.
By the way, as the vibration-preventive support device which is formed of rubber or the like, there are proposed several devices which are disclosed, for example, in Japanese Patent Unexamined Publication No. Hei. 7-37375, Japanese Patent Unexamined Publication No. Hei. 8-63952, and the like. However, in all of them, the device is designed such that it is engaged with a pair of engaging members disposed in a mutually opposing manner within a casing to thereby support a frame and, therefore, the device is complicated in structure.
The present invention aims at eliminating the drawbacks found in the above-described conventional vibration-preventive support devices. Accordingly, it is an object of the invention to provide a vibration-preventive support device which is simple in structure and can provide an excellent vibration damping performance.
In attaining the above object, according to the invention, there is provided a vibration-preventive support device, comprising: an outer cylindrical body to be mounted onto one of two members to be connected together, the outer cylindrical body being formed of elastic material; an inner cylindrical body disposed within the outer cylindrical body to be mounted onto the other member movable with respect to the one member, the inner cylindrical body being formed of elastic material; and a vibration absorbing body formed of elastic material and disposed such that the two ends thereof are respectively connected to one end side end edge of the outer cylindrical body and the other end side end edge of the inner cylindrical body.
According to this structure, since the two ends of the vibration absorbing body are respectively connected to one end side end edge of the outer cylindrical body and the other end side end edge of the inner cylindrical body, out of the two members to be connected and supported, the movable-side member can be supported in such a manner that it is hung. Thanks to this, not only there is eliminated the need for provision of an auxiliary spring which has been conventionally used when the movable-side member is lifted up and supported, but also vibrations can be effectively absorbed by the vibration absorbing body, which makes it possible to connect and support the two members in a vibration-preventive manner.